In mid-1954 International introduced the new low-priced One-Hundred series, $50 cheaper than the standard R-110 pickup. The company promoted the new economy and driving ease of the One-Hundred even though it was almost identical to a basic short-wheelbase R-110. The One-Hundred series came as the R-100 model (4,200 lb GVW) and the R-102 (4,600 lb GVW). The engine was the 104-hp Silver Diamond SD-220 and the only transmission available initially was a 3-speed syncromesh. Shortly after introduction, overdrive and the Metro-Matic 3-speed automatic were added to the option list. The engine output was increased to 108 hp by mid-1955.

For 1956 the light-duty R-series evolved into the S-series. The cab was unchanged but the front end was restyled. The horizontal bar of the old grille was replaced by an oval ring inside a larger trapezoidal opening and the parking lights were mounted on the ring. The headlights were moved to the top front of the fenders where they protruded slightly from the now forward-leaning fenders. The S-100 series came in the basic S-100 model, with unchanged 4,200 lb GVW, and the S-102, with the GVW up to 5,000 lb. Standard equipment in both models was the 108-hp Black Diamond BD-220 engine (a renamed Silver Diamond SD-220) and 3-speed syncromesh transmission. The 131-hp Black Diamond BD-240 was optional for the first time in the 100-series. Optional transmissions were a 3-speed with overdrive or a 3-speed automatic. The standard tires were 6.70-15 4-ply passenger car type with 7.10-15 6-ply optional.